1. Field of the Invention
This invention is directed to ported tubular members; to such tubulars for use in a wellbore; to a fluid port with a metal-to-metal seal; to port closing systems; and to stage tools for use in wellbores.
2. Description of Related Art
Various downhole tools used in the oil and gas industry provide a fluid passageway from inside a conduit (casing or tubing), through its wall, and then outside of the conduit. This passageway is initially open and then closed, or is initially closed then opened. The object is to provide a "gateway" for fluid transfer from inside a conduit to outside. This gateway is found on many tools such as including but not limited to port collars, stage tools, combination packoff stage tools, liner sleeves, and sliding sleeves. It is desirable for this type of gateway that it be effectively sealed once closed; for example, when the gateway is incorporated into a conduit which is subsequently cemented into place such as oil and gas well casing. This conduit is meant to be a permanent placement of a pressure barrier into the earth, sealing off potentially harmful fluids and dangerous pressure. If a gateway leaks after being closed, substantial costs are incurred in retrieving the cemented casing. Typically, relatively affordable polymeric seals are utilized in these types of downhole products.
A drilled wellbore hole is prepared for oil or gas production by cementing casing, liners or similar conduit strings in the wellbore. Cementing is the process of mixing a composition including cement and water and pumping the resulting slurry down through the well casing and back up into the annulus between the casing and the wellbore. Cementing of the annulus provides protection from the intermixing of the contents of various production zones which could result in undesirable contamination of produced oil or gas or in contamination of the producing strata.
In the early days of the oil field industry, the shallower wells allowed cementation to be accomplished by pumping a cement slurry down the well casing, out the casing bottom, and back up the annular space between the bore hole and casing. As wells were drilled deeper, the cementing process was accomplished in two or even three stages. Cementing tools, stage tools, or ported collars equipped with internal valving, were used for multi-stage cementation. Typically, the internal valving of cementing tools, or stage tools, consist of one or more sliding sleeve valves for the opening and closing of the cement ports before and after a cement slurry has passed through the ports. A variety of plugs are used to aid multi-stage cementing to open and close the correct sleeve valve at the correct time.
The sleeve valves are typically shear-pinned in an upper position with the lowermost sleeve sealing the ports closed for running in the wellbore hole. When stage cementing is desired, an opening plug is moved, or dropped and gravitated, to seat and seal off the lowermost sleeve. Pressure applied at the surface applies enough downward force on the plug and seat arrangement to break the shear pins and shift the lower sleeve valve down, thus opening ports which allow cementing solutions or slurries to flow down the interior of the casing and then through the ports into the annulus between the exterior of the casing and the interior of the wellbore. Cement is pumped down the casing, through the ports and back up the annulus.
As the tail end of the cement slurry is pumped down the casing, a second plug often called a "closing plug" is placed into the casing behind the cement. This plug moves down to seat and seal off the uppermost sleeve valve until sufficient surface casing pressure is applied to break the shear pins holding the sleeve. The upper sleeve and plug shift downward to cover and seal off the ports so that no more solution or slurry passes either into the annulus or back from the annulus. An engaging mechanism has been used to lock the closing sleeve in position.
Prior art downhole tools such as safety valves have incorporated into their design valving components which shut off flow through a passageway. Such safety valves usually have control line tubing which routes hydraulic fluid for controlling the valve through a particular passageway. This passageway may allow fluid downhole to another valve for alternate valve operation. When a lower valve is no longer required, the passageway is required to be terminated. One method of termination utilizes a metal plunger and polished seal bore. Hydraulic fluid travels around the plunger and into the seal bore and on downstream to further perform a function. Once the passageway is no longer desired, the metal plunger is forceably driven into the bore, sealing off the passageway. This method is unsatisfactory due to the high degree of smoothness, as well as the tight tolerances required for an interference metal-to-metal seal. In addition, such closure mechanisms are susceptible to damage on their smooth sealing surfaces under abrasive flow. Interference plungers may not provide enough metal flow for total filling of all minute scratches and abrasions inherent with this mechanism.
Another method of terminating the passageway in a valve is to crimp and sever a control line as in U.S. Pat. No. 4,981,177. This method requires crimping and severing of the control line to occur substantially simultaneously.
There has long been a need for ported tubular members in which the port(s) may be efficiently and effectively sealed. There has long been a need for such members in which a metal-to-metal seal is created. There has long been a need for a stage tool with such ports.